U.S. patent application number 12/626594 was filed with the patent office on 2011-05-26 for structural health monitoring system having integrated power supply.
Invention is credited to Irene J. Li, Xinlin Qing, Chang Zhang.
Application Number | 20110125417 12/626594 |
Document ID | / |
Family ID | 44062703 |
Filed Date | 2011-05-26 |
United States Patent
Application |
20110125417 |
Kind Code |
A1 |
Qing; Xinlin ; et
al. |
May 26, 2011 |
STRUCTURAL HEALTH MONITORING SYSTEM HAVING INTEGRATED POWER
SUPPLY
Abstract
A self-sufficient structural health monitoring system that can
monitor a structure without need for external power input.
Embodiments of the invention provide a structural health monitoring
system with a power supply integrated within, so that the system
relies on itself for operational power. Systems with such an
on-board electrical power source, independent of an external power
source (and in particular, independent of the power system(s) of
the structure being monitored), are much more self-contained and
self-sufficient.
Inventors: |
Qing; Xinlin; (Cupertino,
CA) ; Li; Irene J.; (Stanford, CA) ; Zhang;
Chang; (Santa Clara, CA) |
Family ID: |
44062703 |
Appl. No.: |
12/626594 |
Filed: |
November 25, 2009 |
Current U.S.
Class: |
702/34 ; 320/101;
320/128 |
Current CPC
Class: |
G01D 9/005 20130101;
H02J 7/35 20130101 |
Class at
Publication: |
702/34 ; 320/128;
320/101 |
International
Class: |
G06F 19/00 20060101
G06F019/00; H02J 7/00 20060101 H02J007/00 |
Claims
1. A self-powered structural health monitoring system, comprising:
an analyzer operable on electrical power, so as to perform at least
one of: receiving diagnostic signals from a plurality of sensing
elements, the diagnostic signals corresponding to stress waves
detected from a structure by the plurality of sensing elements; and
transmitting querying signals to the plurality of sensing elements,
so as to generate stress waves in the structure; and a rechargeable
power supply in electrical communication with the analyzer and
providing the electrical power to the analyzer; wherein the
rechargeable power supply further comprises a rechargeable battery,
and a generator in electrical communication with the rechargeable
battery and configured to recharge the rechargeable battery.
2. The system of claim 1, wherein the rechargeable power supply
further comprises: a charging circuit connected between the
rechargeable battery and the generator, the charging circuit
operable to convert first electrical signals from the generator to
second electrical signals suitable for recharging the rechargeable
battery; and a substrate having the rechargeable battery and the
charging circuit affixed thereon.
3. The system of claim 2, wherein the electrical power has a first
voltage, and wherein the rechargeable power supply further
comprises: a conversion circuit affixed to the substrate and
connected between the rechargeable battery and the analyzer, the
conversion circuit operable to convert electrical signals produced
by the rechargeable battery at a second voltage to the electrical
power at the first voltage; and a regulator circuit affixed to the
substrate and operable to attenuate a noise in the electrical
signals produced by the rechargeable battery.
4. The system of claim 1, wherein the analyzer further comprises: a
signal conditioning circuit operable on the electrical power to
attenuate a noise in the received diagnostic signals, the received
diagnostic signals being analog signals; an analog to digital
conversion circuit operable on the electrical power to convert the
analog, noise-attenuated, received diagnostic signals to digital
diagnostic signals; and a processor operable on the electrical
power to receive the digital diagnostic signals and to output
signals facilitating a diagnosis of a health of the structure.
5. The system of claim 4, wherein the analyzer further comprises a
voltage transmission circuit operable to receive the electrical
power and to generate the querying signals from the received
electrical power.
6. The system of claim 1, wherein the generator is a solar power
generator.
7. The system of claim 1, wherein the generator is a thermoelectric
power generator.
8. The system of claim 1, wherein the generator is operable to
receive the diagnostic signals from the plurality of sensing
elements, and to recharge the rechargeable battery according to the
received diagnostic signals.
9. The system of claim 1, wherein the generator further comprises
an adapter circuit configured to convert alternating current to
direct current, and configured to recharge the rechargeable battery
according to the direct current.
10. The system of claim 1, wherein the analyzer is operable on the
electrical power to perform both the receiving and the
transmitting.
11. The system of claim 1, further comprising an enclosure having
the rechargeable battery and the analyzer mounted therein.
12. The system of claim 1, wherein the analyzer and the
rechargeable power supply are affixed to the structure.
13. A self-sufficient structural health monitoring system,
comprising: a rechargeable battery; structural health monitoring
diagnostic hardware operable on electrical power from the
rechargeable battery to perform at least one of: receiving
monitoring signals from a plurality of sensing elements, the
monitoring signals corresponding to stress waves detected from a
structure by the plurality of sensing elements; and transmitting
interrogating signals to the plurality of sensing elements, so as
to generate stress waves in the structure; and a generator operable
to recharge the rechargeable battery.
14. The system of claim 13, further comprising: a charging circuit
connected between the rechargeable battery and the generator, the
charging circuit operable to convert first electrical signals from
the generator to second electrical signals suitable for recharging
the rechargeable battery; and a substrate having the rechargeable
battery and the charging circuit affixed thereon.
15. The system of claim 14, wherein the electrical power has a
first voltage, and wherein the rechargeable power supply further
comprises: a conversion circuit affixed to the substrate and
connected between the rechargeable battery and the diagnostic
hardware, the conversion circuit operable to convert electrical
signals produced by the rechargeable battery at a second voltage to
the electrical power at the first voltage; and a regulator circuit
affixed to the substrate and operable to attenuate a noise in the
electrical signals produced by the rechargeable battery.
16. The system of claim 13, wherein the diagnostic hardware further
comprises: a signal conditioning circuit operable on the electrical
power to attenuate a noise in the received diagnostic signals, the
received diagnostic signals being analog signals; an analog to
digital conversion circuit operable on the electrical power to
convert the analog, noise-attenuated, received diagnostic signals
to digital diagnostic signals; and a processor operable on the
electrical power to receive the digital diagnostic signals and to
output signals facilitating a diagnosis of a health of the
structure.
17. The system of claim 16, wherein the analyzer further comprises
a voltage transmission circuit operable to receive the electrical
power and to generate the interrogating signals from the received
electrical power.
18. The system of claim 13, wherein the generator is a solar power
generator.
19. The system of claim 13, wherein the generator is a
thermoelectric power generator.
20. The system of claim 13, wherein the generator is operable to
receive the diagnostic signals from the plurality of sensing
elements, and to recharge the rechargeable battery according to the
received diagnostic signals.
21. The system of claim 13, wherein the generator further comprises
an adapter circuit configured to convert alternating current to
direct current, and configured to recharge the rechargeable battery
according to the direct current.
22. The system of claim 13, wherein the diagnostic hardware is
operable on the electrical power to perform both the receiving and
the transmitting.
23. The system of claim 13, further comprising an enclosure having
the rechargeable battery and the diagnostic hardware mounted
therein.
24. The system of claim 13, wherein the diagnostic hardware and the
rechargeable battery are affixed to the structure.
Description
BRIEF DESCRIPTION OF THE INVENTION
[0001] This invention relates generally to structural health
monitoring. More specifically, this invention relates to structural
health monitoring systems with integrated power supplies.
BACKGROUND
[0002] The structural health monitoring field often aims at
carrying out the diagnostics and monitoring of structures using
sensor arrays connected to associated hardware, such as dedicated
analyzers. When connected to a computer, this hardware can allow
users to determine the integrity of structures, often in, or close
to, real time. In this manner, structural health monitoring systems
and techniques can go beyond simple detection of structural
failure, to providing additional useful information such as early
indications of damage.
[0003] However, structural health monitoring systems still suffer
from drawbacks. For example, the analyzers and other computational
devices employed commonly require electrical power provided by an
external electrical power source. For some applications requiring
placement of hardware remote from typical power sources, such as
aviation and combat vehicles, this may present a severe impediment
to use of such hardware.
SUMMARY
[0004] The invention can be implemented in a number of ways, such
as by a system.
[0005] In one embodiment, a self-powered structural health
monitoring system comprises an analyzer operable on electrical
power, so as to perform at least one of: receiving diagnostic
signals from a plurality of sensing elements, the diagnostic
signals corresponding to stress waves detected from a structure by
the plurality of sensing elements; and transmitting querying
signals to the plurality of sensing elements, so as to generate
stress waves in the structure. The system also includes a
rechargeable power supply in electrical communication with the
analyzer and providing the electrical power to the analyzer. The
rechargeable power supply further comprises a rechargeable battery,
and a generator in electrical communication with the rechargeable
battery and configured to recharge the rechargeable battery.
[0006] In another embodiment, a self-sufficient structural health
monitoring system comprises a rechargeable battery, and structural
health monitoring diagnostic hardware operable on electrical power
from the rechargeable battery to perform at least one of: receiving
monitoring signals from a plurality of sensing elements, the
monitoring signals corresponding to stress waves detected from a
structure by the plurality of sensing elements; and transmitting
interrogating signals to the plurality of sensing elements, so as
to generate stress waves in the structure. The system also includes
a generator operable to recharge the rechargeable battery.
[0007] Other aspects and advantages of the invention will become
apparent from the following detailed description taken in
conjunction with the accompanying drawings which illustrate, by way
of example, the principles of the invention.
BRIEF DESCRIPTION OF THE DRAWINGS
[0008] For a better understanding of the invention, reference
should be made to the following detailed description taken in
conjunction with the accompanying drawings, in which:
[0009] FIG. 1 is a block diagram depiction of an exemplary
structural health monitoring system according to embodiments of the
present invention;
[0010] FIG. 2 is a block diagram depiction illustrating further
details of the battery pack block of FIG. 1;
[0011] FIG. 3 is a block diagram depiction illustrating further
details of active structural health monitoring diagnostic hardware
that can be employed;
[0012] FIG. 4 is a block diagram depiction illustrating further
details of passive structural health monitoring diagnostic hardware
that can be employed; and
[0013] FIG. 5 illustrates various different energy harvesters that
can be employed in connection with the battery pack block of FIG.
1.
[0014] Like reference numerals refer to corresponding parts
throughout the drawings.
DETAILED DESCRIPTION OF EMBODIMENTS OF THE INVENTION
[0015] In one embodiment, the invention relates to a
self-sufficient structural health monitoring system that can
monitor a structure without need for external power input. That is,
embodiments of the invention provide a structural health monitoring
system with a power supply integrated within, so that the system
relies only on itself for operational power. Systems with such an
on-board electrical power source, independent of an external power
source (and in particular, independent of the power system(s) of
the structure being monitored), are much more self-contained and
self-sufficient.
[0016] In particular, embodiments include systems that have a
network of sensors, analyzer, and a rechargeable power supply
(e.g., a rechargeable battery) that includes an energy harvesting
device. This energy harvesting device recharges the battery, thus
providing the system with its own continuous source of electrical
power. The energy harvesting device is preferably a lightweight,
portable generator that can generate electrical power sufficient to
recharge the battery, and can be any appropriate form of generator.
Embodiments include generators that are solar power generators,
thermoelectric generators, and generators that harvest
piezoelectric vibration energy from the sensor network.
[0017] Any one or more of the sensors, analyzer, and power supply
may be affixed to, or otherwise located on, the structure. It can
thus be seen that embodiments of the invention allow for a
self-sufficient system that monitors a structure under its own
power, requiring only a relatively small, lightweight portable
generator to recharge the battery from time to time.
[0018] FIG. 1 is a block diagram depiction of an exemplary
structural health monitoring system according to embodiments of the
present invention. The structural health monitoring system 10
includes a sensor network 20 connected to diagnostic hardware 30,
where the sensor network 20 has multiple sensing elements that are
affixed to a structure. The sensing elements of sensor network 20
monitor the structure and transmit information to the diagnostic
hardware 30, which in turn interfaces with host computer 40. The
diagnostic hardware 30 is an analyzer that can be configured to
process transmitted information from the sensing elements (such as
by determining impact severity/location from signals received from
the sensing elements), or can be configured to only perform tasks
such as switching between different sensing elements, while routing
sensor information to the host computer 40 for processing/analysis.
That is, the invention includes embodiments in which the diagnostic
hardware 30 only passes signals to/from the sensor network 20
(perhaps after conditioning), and embodiments in which the hardware
30 performs some or all of the calculations involved in determining
structural health.
[0019] The sensing elements of sensor network 20 can be any set of
sensors and/or actuators capable of detecting and transmitting
stress waves, respectively. Typically, a sensor network 20 includes
multiple actuating and/or sensing elements placed at discrete
locations on the structure, for transmitting stress waves through a
structure and detecting resulting waveforms, respectively. As is
known, sensors can both passively monitor a structure for stress
waves resulting from an impact (whereupon analysis of such stress
waveforms can be performed to determine data about any
corresponding damage), and monitor the structure for stress waves
actively transmitted through the structure by the actuators
(whereupon comparison of the resulting waveforms to the original
signals transmitted can indicate damage). The invention
contemplates use of any sensors and any actuators, affixed to a
structure in any manner and any number that allow for evaluation of
the structure. However, one suitable sensor/actuator is lead
zirconate titanate (PZT) piezoelectric transducers (or any other
suitable transducer) that each can act as both a sensor and an
actuator. In known manner, each PZT transducer converts electrical
signals to stress waves in order to actively query a structure, and
converts resulting detected stress waves to electrical signals for
analysis.
[0020] Furthermore, the sensors/actuators can be individually
affixed to a structure, or affixed to a flexible diagnostic layer
that can itself be affixed to a structure. This diagnostic layer
and its operation are further described in U.S. Pat. No. 6,370,964
to Chang et al., which is hereby incorporated by reference in its
entirety and for all purposes. Construction of the diagnostic layer
is also explained in U.S. Pat. No. 7,413,919 to Qing et al., which
is also incorporated by reference in its entirety and for all
purposes.
[0021] The structural health monitoring system 10 also includes a
battery pack 50 and energy harvesting device 60. The battery pack
50 preferably supplies power sufficient to operate the diagnostic
hardware 30 and sensor network 20, while also being sufficiently
small and lightweight to be located on, or perhaps in, the
structure being monitored. That is, the battery pack 50 supplies
sufficient power to run the sensor network 20 and hardware 30,
while also accompanying the network 20 and hardware 30. In
particular, embodiments of the invention employ a battery pack 50
that can supply enough power to operate network 20 and hardware 30
without compromising the performance of the structure or its
user(s), and without compromising the ability to locate the network
20 and hardware 30 in many places along the structure.
[0022] The energy harvesting device 60 can be any device capable of
recharging the battery pack 50. However, device 60 is preferably an
electrical generator that is small and lightweight enough so that
it does not significantly interfere with the use/operation of the
structure or its user, or can relatively easily accompany the
remaining components of the system 10 and be connected to the
battery pack 50 when needed. Further details of the energy
harvesting device 60 are provided below.
[0023] FIG. 2 is a block diagram depiction illustrating further
details of the battery pack 50. The battery pack 50 includes a
rechargeable battery 110 and various associated circuitry. Here,
the battery pack 50 includes a DC voltage conversion circuit 100,
power regulation circuit 120, battery charger 130, battery monitor
140, and indicator 150. The DC voltage conversion circuit 100 is
connected between the rechargeable battery 110 and diagnostic
hardware 30, and converts voltage from the battery 110 to the
correct voltage levels required for operation of the components of
hardware 30. The power regulation circuit 120 is also connected
between the rechargeable battery 110 and diagnostic hardware 30,
and conditions the battery output to provide a more stable power
supply. For example, the power regulation circuit 120 can contain
known circuits such as filters for noise reduction. The battery
charger 130 is another conversion circuit that converts power from
the energy harvesting device 60 to the voltage/current desired for
recharging the battery 110. The battery monitor circuit 140
monitors charge levels of the battery 110 and, if too low,
indicator 150 lights up to indicate low battery charge. The
conversion circuit 100, regulation circuit 120, charger 130,
monitor circuit 140, and indicator 150 can be made of known
circuits and devices.
[0024] For improved robustness and resistance to damage, any one or
more of the sensor network 20, diagnostic hardware 30, host
computer 40, battery pack 50, and energy harvesting device 60 can
be mounted within a single enclosure, such as a rigid metal casing
suitable for mounting electronics within. Furthermore, any
combination of the sensor network 20, hardware 30, and battery pack
50, whether in a casing or not, can be affixed to the structure
being monitored.
[0025] FIG. 2 also shows two different possible energy harvesting
devices 60, i.e., power sources. Here, both an energy harvesting
device 160 (which can be a solar energy harvesting device, as
shown) and AC/DC adapter 170 are shown. Either device can be
employed to charge the battery 110, and the energy harvesting
device 60 can include any one or more (as well as others), although
it is anticipated that only one such device 160, 170 will be
employed at a time. The AC/DC adapter 170 is a known adapter for
converting standard 110 V AC power to DC power suitable for
recharging battery 110, and allows the system 10 to be plugged in
to a "standard" outlet. This gives users the ability to recharge
their battery 110 at any location with a power outlet, for added
convenience and ease of use. While the adapter 170 is described
here as a 110 V AC power to DC power adapter, embodiments of the
invention contemplate an adapter configured to convert any AC power
source to any DC power level suitable for charging a battery.
Furthermore, embodiments of the invention contemplate any battery
110 with any voltage level suitable for use with system 10.
[0026] It is also noted that embodiments of the invention
contemplate any form of diagnostic hardware 30 that can operate
solely, or substantially solely, on power from battery pack 50. In
particular, the invention contemplates both diagnostic hardware 30
that can actively interrogate or query a structure, and hardware 30
that passively monitors the structure. That is, the invention
contemplates diagnostic hardware 30 capable of directing the
transmission of predetermined diagnostic stress waves through the
structure, and detecting those same stress waves after they have
propagated through the structure, so that structural health can be
determined according to how those stress waves have changed. The
invention also contemplates hardware 30 that is only capable of
passive monitoring, i.e., capable of detecting stress waves, but
not capable of generating them.
[0027] Various embodiments of the invention also include
configurations in which any one or more of the diagnostic hardware
30, host computer 40 or any portion thereof, battery pack 50,
and/or energy harvester 60 are mounted on a single substrate, such
as a printed circuit board (PCB) or the like. In this manner,
system 10 can be made more convenient, and easier, to transport or
install.
[0028] FIG. 3 is a block diagram depiction illustrating further
details of an embodiment of diagnostic hardware 30 capable of
active interrogation of a structure. The diagnostic hardware 30
includes a high voltage transmitter and converter 200 for
transmitting higher-voltage actuation signals to the sensing
elements of network 20 (used by the sensing elements to generate
interrogating stress wave pulses in the structure), a high voltage
switch 202, and A/D converter 204 for converting the lower-voltage
signals (sent from the sensing elements when they detect stress
waves in the structure). Hardware 30 also includes a data buffer
206 for buffering digital signals from the A/D converter 204, and
controller 208. The various components of hardware 30 are
interconnected, and communicate with each other, as shown.
[0029] The various components of diagnostic hardware 30 run on
electrical power that is supplied by battery pack 50. As in FIGS.
1-2, the battery pack 50 includes a rechargeable battery 110 that
supplies the power used to operate hardware 30. In particular, the
battery 110 supplies sufficient power to allow the high voltage
transmitter and converter 200 to transmit high-voltage pulses to
the sensor network 20. As above, the battery 110 is recharged by
energy harvest device 210 and battery charger 130. The battery 110
can also be recharged by plugging AC/DC adapter 170 into an outlet.
The energy harvest device 210 can be any relatively portable source
of electrical power. Exemplary types of such devices 210 are
further described below.
[0030] Operation of the diagnostic hardware 30 of FIG. 3 includes
operation in both active (sending stress waves through the
structure) and passive (detecting stress waves in the structure)
modes. In active mode, the high voltage transmitter and converter
200 receives an instruction initiated by either the host computer
40 (through the controller 208) or the controller 208, directing it
to transmit high voltage pulses having a predetermined waveform. In
response, the transmitter and controller 200 transmits a
corresponding high voltage pulse waveform. The host computer 40 or
controller 208 also directs the high voltage switch 202 to
electrically connect the transmitter and converter 200 to those
sensing elements of the sensor network 20 that are to transmit the
stress waves through the structure. Accordingly, the high voltage
pulse waveforms from transmitter and converter 200 are sent to
specified sensing elements, whereupon those sensing elements
convert the voltage waveforms to corresponding stress waveforms in
the structure. These interrogating or querying waveforms propagate
through the structure and are detected by other (or the same)
sensing elements, where changes in the waveforms can indicate
changes in the structure. The sensing elements convert these
detected waveforms to electrical signals which are transmitted to
hardware 30 and processed as in passive mode.
[0031] FIG. 4 is a block diagram depiction illustrating further
details of an embodiment of diagnostic hardware 30 capable of
operation in passive mode. In this embodiment, the diagnostic
hardware 30 includes rechargeable battery 110 supplying power to
processor 300, A/D converter 320, multiplexer 330, and signal
conditioning circuit 340. The diagnostic hardware 30 also includes
an RF transmitter 310, if desired. The various components are
connected as shown.
[0032] In passive mode operation, the hardware 30 detects stress
waves propagating through the structure. Sensing elements in sensor
network 20 detect stress waves and convert them to electrical
signals that are conditioned (e.g., noise filtered and amplified)
by conditioning circuit 340. Multiplexer 330 is set (by processor
300 and/or host computer 40) to receive signals from specified
sensing elements, so that only conditioned sensor signals from
those specified sensing elements are transmitted from the
multiplexer 330 to A/D converter 320. The A/D converter 320 then
converts these analog sensor signals to digital signals and
transmits them to the CPU 300 for processing and/or forwarding to
host computer 40 (not shown). Forwarding can be accomplished in any
manner, but in the embodiment shown, the processor 30 transmits
sensor signals and/or processed data to RF transmitter 310 for
wireless transmission to host computer 40. As with the embodiment
of FIG. 3, the processor 300 can be configured to process the
sensor signals it receives, generating any desired structural
health monitoring data. For example, the processor 300 can
determine damage locations and severities, etc.
[0033] The processor 300 can also be configured only to forward its
received sensor signals to host computer 40, so that host computer
40 is responsible for calculating any desired structural health
monitoring quantities. Additionally, the processor 300 can be
configured for any combination of these two (e.g., determining any
intermediate quantities), or for performing other tasks, such as
transmitting sensor signals/data to multiple different host
computers 40, determining the timing of such transmissions, etc.
Also, it should be noted that the "active mode" version of hardware
30 is also configured to operate in passive mode, i.e. it can both
transmit stress waves through the structure, and monitor the
structure to detect stress waves. The invention encompasses
embodiments in which hardware 30 is configured to operate in purely
active mode, purely passive mode, or a combination of the two, as
desired.
[0034] It should also be noted that the battery 110 of the
embodiment of FIG. 4 is integrated with the diagnostic hardware 30.
However, as in FIGS. 1-2, the invention also contemplates
embodiments in which the battery 110 is located in the battery pack
50. The invention contemplates location of the battery 110 in any
suitable location and within any component, so long as the battery
110 can provide sufficient power for operation of diagnostic
hardware 30. Often, the location or degree of integration of the
battery 110 with other components can depend on what is convenient
for different applications.
[0035] The structure and operation of the diagnostic hardware 30
and battery pack 50 having been explained, attention now turns to a
further description of the energy harvester 60. FIG. 5 illustrates
different energy harvesters that can be employed in connection with
various embodiments of the invention. As examples, the energy
harvesting device 60 can be any one or more of a piezoelectric
vibration generator 400, a solar power module 410, or a
thermoelectric generator 420, each of which will be further
described below. Each of these generators 400-420 is a relatively
small, portable generator that can provide sufficient power to
recharge battery 110, thus supplying enough power to render the
structural health monitoring system 430 (which can include sensor
network 20, diagnostic hardware 30, and/or host computer 40)
self-sufficient in the sense that it does not require any
additional electrical power.
[0036] The vibration generator 400 is connectable to the output of
the sensor network 20, and contains adapters and electrical storage
sufficient to store charge generated by signals output from the
sensing elements of sensor network 20. That is, stress waves in the
structure are converted to electrical signals by the sensing
elements, and the generator 400 harvests these signals to generate
power for recharging the battery 110. In this manner, the sensing
elements can be thought of as converting stress waves from the
structure to electrical power which is harvested by generator 400
to recharge the battery 110.
[0037] In embodiments in which the sensing elements are
piezoelectric transducers, the vibration generator 400 is a
piezoelectric vibration generator 400 (as shown in FIG. 5), where
the transducers convert received stress waves to electrical
signals. At times when these transducers are not used to monitor
the structure, their electrical signals can instead be stored by
generator 400 and used to recharge the battery 110. The generator
400 can thus employ known components such as accumulators,
capacitors, or other charge storage devices, as well as circuitry
for converting this stored charge to the correct voltage for
recharging battery 110. Typical operation of the generator 400
would thus include placing an input of the generator 400 in
electrical communication with the output of sensor network 20
(perhaps when the network 20 is not used to monitor the structure,
and via any output, such as one constructed at a boundary of the
network 20 or in another component such as the hardware 30),
charging a storage device from the electrical signals output by the
sensor network 20, and converting the stored charge to recharge the
battery 110.
[0038] The solar power module 410 is any suitable solar power
generator, but is often preferably a small, lightweight solar panel
assembly. This solar panel is preferably sufficiently portable to
accompany the system 10, and preferably has an interface allowing
for relatively easy connection to the battery pack 50 when the
indicator light 150 indicates that the battery 110 needs to be
recharged. The solar power module 410 can utilize any form of solar
cell that is sufficiently portable. Examples include lightweight,
and possibly flexible, panels made from thin film solar cells,
crystalline solar cells, and the like. The construction and
operation of such solar panels are known.
[0039] The thermoelectric generator 420 can be any device
converting a temperature difference to an electrical voltage, such
as by the Peltier-Seebeck or Thomson effects. In one embodiment,
the thermoelectric generator 420 can utilize a small heater and a
set of thermocouples to effectively convert heat from the heater to
a voltage that can be used to recharge the battery 110. Examples of
this configuration include radioisotope thermoelectric generators
that utilize radioactive material as the heater, thermoelectric
generators that harness waste heat from the structure itself as a
heat source, or any other thermoelectric generator that is
sufficiently small and lightweight to accompany system 10.
[0040] It should be noted that the invention includes embodiments
in which each energy harvester 60 utilizes a single generator
400-420, which can be any of the generators described above.
However, the invention also includes embodiments in which multiple
different generators 400-420 are used in a single energy harvesting
device 60. For instance, in embodiments in which piezoelectric
vibration generator 400 does not generate sufficient power to
recharge battery 110 by itself, an additional solar power module
410 may be employed. The invention contemplates harvesters 60 that
incorporate any number and combination of generators 400-420.
[0041] It should also be noted that it is preferable to employ
batteries 110 capable of sustaining an output power level equal to
or greater than the power required to operate sensor network 20 and
diagnostic hardware 30. For example, while past diagnostic hardware
has required excessive power to operate, the capability has been
recently developed to construct diagnostic hardware 30 that uses
approximately 5 W of power, in part due to use of new, low-power
processors that can be used as a controller 208 or CPU 300. For
such hardware 30, a battery such as an OceanServer.TM. Technology,
Inc. BA95HC-FL battery, rated at 14.4 Volts, 95 Watt-hours, and
6600 milliamp-hours, can be employed in battery pack 50.
[0042] The foregoing description, for purposes of explanation, used
specific nomenclature to provide a thorough understanding of the
invention. However, it will be apparent to one skilled in the art
that the specific details are not required in order to practice the
invention. Thus, the foregoing descriptions of specific embodiments
of the present invention are presented for purposes of illustration
and description. They are not intended to be exhaustive or to limit
the invention to the precise forms disclosed. Many modifications
and variations are possible in view of the above teachings. For
example, the energy harvesting device 60 can be any relatively
lightweight, portable source of electrical power, such as a
lightweight solar cell panel, a circuit that stores power from the
sensor network 20, or a relatively small thermoelectric generator.
These sensors/actuators can be located on a flexible substrate or
individually placed, and they (along with their substrate, if one
is employed) can be affixed to an outer surface of a structure or
embedded within. The embodiments were chosen and described in order
to best explain the principles of the invention and its practical
applications, to thereby enable others skilled in the art to best
utilize the invention and various embodiments with various
modifications as are suited to the particular use contemplated.
* * * * *